The present invention relates to power supply systems. More specifically, the present invention relates to a power supply mounting system for a high density printed circuit board.
All alternating current (AC) powered electronic equipment contain one or more power supplies to convert the AC input power to various lower direct current (DC) voltages needed by the circuits inside the equipment. In the prior art, a typical connection of power from the power supply to a printed circuit board (PCB) on which various components such as integrated circuits (IC's) are mounted is by a wire harness. One or more PCBs and peripheral devices have power coupled to them in this manner. In today's complex computers, a single large multilayer printed circuit board is usually included, a so-called motherboard, and one or more large IC's including the microprocessor chip and various memory chips are mounted on this motherboard. Use of a wire harness to couple the power supply to a component on the motherboard has severe limitations as there are significant resistive losses and inductive effects in the wires of the wire harness and conductors in the multilayer PCB. As is known in the art, resistive losses are largely determined by the amount of current in a wire or conductor. Similarly, inductive effects are largely determined by the rate at which current through a wire changes and the length of the wire. Accordingly, the resistive losses and inductive effects are significant in a wire or conductor that delivers power to an IC chip or other component that has a high power demand, especially where the active component operates at a low voltage and has a wide ranging and rapidly changing current demand.
Unfortunately, from the perspective of resistive losses and inductive effects, most modem day microprocessors have a high power demand, a low operating voltage, and a wide ranging and rapidly changing current demand. For example, the Intel Pentium Pro microprocessor operates at 3.1 volts and has a current demand that can change from 0 to 11.2 amps in 350 nanoseconds. It is expected that future microprocessors will operate at voltages as low as 1 volt and will have a current demand of up to 80 amps. This will significantly increase resistive losses and inductive effects in wires and conductors connecting the power supply to the microprocessor. As a result of the resistive losses and the inductance of such power coupling wires or conductors, a power supply with a wire harness is not able to deliver an accurately regulated low voltage to components on the motherboard drawing large transient currents.
In addition to having high resistive losses and inductive effects, wire harnesses are difficult to use. Furthermore, the connectors between the wire harnesses and the components often pose reliability concerns.
The above disadvantages of using wire harnesses are well known in the art and have resulted in the use of distributed power systems in some applications. In a distributed power system, a simple AC to DC power supply produces a single voltage output which is distributed around the system. Typically, the power supply produces a bus voltage of 48 volts. This voltage is preferred because it is low enough to ensure compliance with international safety standards, yet high enough to reduce distribution losses which are proportional to the square of the current. However, other bus voltages, such as 24 or 12 volts, are also possible. The distributed power system also includes one or more high density DC to DC converters (i.e., converters that have a high power output per cubic volume of space that they occupy). These high density DC to DC converters are powered by the bus voltage and are placed in close proximity to the high power demand components powered by the power source. The reduced distance between the high power demand components and the adjacent power converter significantly reduces the resistive losses and the inductive effects in the wires and conductors coupling the power converter to the component.
However, fully distributed power systems are not yet cost effective in high volume, low cost systems, such as personal computer systems. Nonetheless, some components in personal computers require a very fast response from the AC-DC or DC-DC converter to which they are coupled. For example, many high performance processor chips used in personal computers require a fast transient current response from a DC to DC converter providing a tightly regulated programmable output from 1.8 to 3.6 volts to the processor chip. The need for precise voltage regulation by such chips requires use of what is known in the art as a voltage regulator module (VRM). A VRM can be either a complete plug-in DC to DC converter or a circuit implemented on the motherboard. The addition of a VRM to a power system increases the cost of the power system by approximately 50%. Additionally, VRMs occupy valuable motherboard area. This is particularly significant when the "wasted" area under the power converter or VRM is, for example, a portion of a 12-14 layer high density, high cost motherboard.
Another disadvantage of prior art power systems, and more particularly the mounting structure of prior art power systems, is that they typically use mounting structures on which one cannot mount both a power supply and an IC chip module such that the power supply and IC chip module are slidably mounted on the mounting structure and releasably locked thereto. As a result, generally the distance between the power supply and the IC chip module is not minimized and consequently the length of connections for supplying power from the power supply to the IC chip module is also not minimized. Consequently, resistive losses and inductive effects in delivering power from the power supply to the IC chip module are not minimized. Additionally, generally separate heatsinks are used to dissipate heat generated by the IC chip module and the power supply.
Another disadvantage of some prior art mounting structure is the fact that they use a heatsink that is not coupled to the frame of the mounting structure and supported thereby to dissipate heat from the IC chip module powered by the power supply mounted on the mounting structure. Instead, a heatsink that is not connected to the frame is disposed over the IC chip module, which necessitates using support frames for the heatsink as its center of gravity is typically not aligned with that of the socket and the IC chip module to which it is thermally coupled to dissipate heat therefrom.
Therefore, it is desirable to tightly regulate the voltage applied to one or more IC chips mounted on a PCB. It is also desirable to reduce resistive losses and inductive effects in delivering power to components on a PCB. It is also desirable to efficiently utilize the surface area of a printed circuit board. It is also desirable to use a mounting structure upon which one can slidably mount both a power supply and a IC chip module such that the power supply and IC chip module are releasably locked onto the mounting structure and the length of the electrical connection between the power supply and the IC chip module are minimized in order to minimize the resistive losses and inductive effects in delivering power from the power supply to the IC chip module. The releasably locking feature of the present invention allows easy mounting and dismounting of the power supply and IC chip module, which facilitates the replacement of the power supply and IC chip module. It is also desirable to use one heatsink to dissipate heat generated by both the IC chip module and the power supply.